This paper presents a force visualization mechanism for endoscopic surgical instruments using a Moirée fringe. This mechanism can display fringes or characters that correspond to the magnitude of a force between the surgical instruments and internal organs without the use of electronic elements, such as amplifiers and strain gauges. As this mechanism is simply attached to the surgical instruments, there is no need for additional devices in the operating room or wires to connect these devices. The structure is simple, and its fabrication is inexpensive. An example is shown with the mechanism mounted on a 10-mm forceps. We experimentally verified in vivo, using a pig, that it can display characters corresponding to the magnitude of the force, thus visually displaying the force even in endoscopic image.